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Soil health is a pathway through which farm and environmental outcomes can be improved together on agricultural landscapes, and management to improve soil health is increasingly recognized as a strategy for agricultural producers to adapt to climate change–related impacts such as erosion and flooding. Many incentive programs exist or are in development to support the adoption of practices that promote soil health for these reasons, but few on‐farm trials have compared the intersections of farmer versus researcher observations of soil health or of soil health compared with climate adaptation. The purpose of our study was to assess soil health outcomes and adaptation to simulated climate change in response to cover cropping on working farms enrolled in a Minnesota Natural Resources Conservation Service (NRCS)–funded Environmental Quality Incentives Program. This incentive program required the inclusion of diverse cover crop mixtures into existing farm crop rotations. We conducted farmer surveys, NRCS protocol field soil assessments, and NRCS‐recommended laboratory assays on farms from across the state of Minnesota in a paired design comparing fields on the same or adjacent farms of the same soil mapping unit. Although 85% of farmers reported improvements in soil attributes or productivity, most field and laboratory assessments produced a high amount of variability in responsiveness to cover cropping. Despite this variability, we saw a significant decrease in bare ground and significant increases in earthworm counts, cellobiohydrolase microbial activity, and the Visual Evaluation of Soil Structure (VESS). Although researcher measurements did not show improvement in physical characteristics or infiltration other than the VESS field assessment, 67% of farmers reported improvements to the physical structure of the soil, associated with improved outcomes such as earlier planting dates and consistent crop growth across fields. When more than five species of cover crops were present, the percentage of reported improvements increased to >80%. We also found no significant improvement to climate change adaptation measured by nutrient or sediment loss after a simulated storm event. Together, our results suggest that adding a diverse annual cover crop mix to increase continuous cover can improve characteristics associated with soil health and that there needs to be a stronger focus in understanding variation in realized soil health outcomes on farms, including more co‐creation of research with farmer partners.

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Core Ideas Bluegrass cover crop decreased maize productivity compared to rye or no cover crop. Cover crop biomass was greater with silage maize than grain, but net ecosystem carbon balance was negative. Cover crop growth did not offset maize silage removal. Seasonal cover crop rhizosphere priming did not affect net ecosystem carbon balance. Cover crops have potential to increase net ecosystem C balance (NECB) and subsequent accrual of soil organic C (SOC) by lengthening the growing season in annual agriculture. By measuring net primary productivity (NPP) and C lost to harvest and heterotrophic respiration (Rh), our objective was to evaluate NECB of annual (winter rye, Secale cereale L.) and perennial (Kentucky bluegrass, Poa pratensis L.) cover crops compared to no cover crop control in continuous maize (Zea mays L.) harvested for either grain or silage. There was no effect of cover crop on NECB, but grain maize NECB was greater than silage (32 vs. −433 g C m−2), indicating greater SOC sink when maize residue was retained. Rye was more productive in silage (147 g C m−2) compared to grain (32 g C m−2). Rye increased total belowground NPP in silage maize (rye: 326, no cover: 275, bluegrass: 268 g C m−2) but bluegrass decreased aboveground NPP in grain (rye: 1079, no cover: 1179, bluegrass: 1026 g C m−2) and silage (rye: 1037, no cover: 1025, bluegrass: 864 g C m−2). Yield was lower under bluegrass (781 g C m−2) than no cover (962 g C m−2) in silage. Losses of C to Rh varied by year, but not by harvest or cover crop. While cover crops may provide multiple benefits to farmers and society, their capacity to directly increase SOC may be low.